The present invention is directed to devices which provide streams of high temperature gaseous fluid, such as air, or high temperature fluids to systems or items which require the same. For instance, flameless torches are used to solder items, to dry items such as coatings and ink, cure epoxy resin, shrink heat shrinkable film, sterilize air or nitrogen for use in packaging medical products, and the like. Hot fluids are pumped through hoses to cause viscous fluids to flow more easily.
By way of example the present invention is described in connection with a flameless torch, but other devices fit within the invention such as heated hoses and the like. In the past, such flameless torches have been restricted in how high the temperature of the gas might go because of the length of the torch, materials limitations, and because of the high watt density. The foregoing occurs because the flameless torch of the prior art uses a single heating element. In addition, there are failures in the prior art systems because the heating elements burn out, if the gas flow becomes sufficiently reduced or stopped.
The present system has overcome these infirmities because it has a two stage heating arrangement connected to a fast response temperature controller. Large amounts of heat are added to the fluid in the second stage. The present system prevents failures, i.e. burning out the heating elements by having the first stage heater act as a sensor. The electrical current flowing through the first stage heater is in proportional relationship to its resistance. If the gas flow were to stop and the heat rise, the electrical current would be reduced accordingly and such would not result in a burned out element. The second stage heater is connected to "track" the first stage heater so that the second stage heater is not subjected to high current densities if the gas flow is reduced drastically or stopped.